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Dolby Volume And DialNorm


(click thumbnail)Dolby demonstrated its Dolby Volume technology at CES2007. While attending the 2007 Consumer Electronics Show in Las Vegas, I stopped by the Dolby booth to see what was new. I was really interested in the Dolby Headphone product more than anything else. It was brand new at last year's show and the demonstration that I had was quite impressive and I wanted to see how the technology rollout was going. I am pleased to say that there are now a number of manufacturers incorporating Dolby Headphone into their products including a number of laptop manufacturers. There were several multimedia laptops on display that incorporated Dolby Headphone technology in their audio circuitry which can be a great asset as more and more nonlinear editing is moved from the dedicated edit suite at the station to the remote location.

Another product that included Dolby Headphone technology that really caught my attention was the JVC SU-DH1 surround sound headphone adaptor. Though designed for the consumer market space, I can see uses for this at the station level as well. At IPTV we've had many discussions regarding desktop editing options. I am a firm believer that in the not-too-distant future, the majority of our editing will be done at the editors' true desktops and not at desktops built into an edit suite. This arrangement allows the editor to take advantage of the creative moment as opposed to having to wait for a room to become available. I have been in many sessions where much time was spent sitting around waiting for inspiration while many good ideas are lost because they happen outside of the room. The chief concern that I have heard expressed about editing at the desktop is the spillover of audio in and out of the workspace. I have always maintained that headphones are a viable solution and the addition of an adaptor like the SU-DH1 allows the editor to make creative decisions regarding surround sound audio without the need of a true sound booth. Now I am not claiming that Dolby Headphone is the perfect substitute for true surround sound but it does provide a very accurate representation and with a suggested list price of $129.95, the SU-DH1 is a good alternative.


At this point, I honestly thought I was done with Dolby but the next morning there was a press release announcing a new product for the consumer market space called Dolby Volume and thus started a small maelstrom. I didn't see the original press release but I did read a newsletter story that described the Dolby Volume process and seemed to imply that since Dolby's dialog normalization has not found industry-wide acceptance, this was a different approach that Dolby was attempting. Regular readers of my column may remember about a year ago I did some tests on the terrestrial DTV service in the Des Moines area and measured the loudness of all the DTV stations in the market. The results were that only IPTV and one other station were adhering to dialnorm and the other stations were all over the board when it came to volume between each other as well as their own local and network sources. Could Dolby Volume actually fix the problem of loud commercials, level variations between channels and eliminate the need for dialog normalization? It sounded too good to be true and I believe it is too good to be true.

The beauty of dialog normalization is that the intelligence for how to handle it is included with the metadata in the audio. It maintains a consistent audio level for dialog while allowing more dynamic departures for music and effects. From what I could tell, Dolby Volume is a completely single-ended technology that acts as an intelligent limiter but I couldn't see how it would negate the advantages of dialog normalization. I set up a call with Jeff Riedmiller from Dolby to see if I could get the full story. I have been acquainted with Jeff for a few years and he has presented at the Iowa DTV Symposium and quite frankly, if there is something here that is revolutionary, I wanted to see if he'd present it at the next DTV Symposium. Jeff and I spoke briefly and a few days later he and I were on another call with Rocky Graham, also from Dolby. Here is what we discussed on those two calls.


The first question was, Does Dolby Volume make dialog normalization unnecessary?

The answer is no. According to Jeff, the best way to maintain accurate volume control and pristine aural quality is to use metadata and dialog normalization. The handshake that is inherent between the content creator and the content presentation system provides the best quality audio possible. Dolby Volume is a single-ended technology designed to be placed in the consumer device and compensate for non-metadata and analog services. The examples we discussed were gaming, analog services and MPEG 1-Level 2 audio systems.

How are the two systems different? Aside from the differences above, Dolby Volume acts as an intelligent limiter but it does do some dynamic range compression. In the absence of metadata, the idea is to keep the perceived aural spectral range consistent and provide for balance when the levels abruptly change; like when a loud commercial appears or the viewer changes channels.

Will the two technologies be able to coexist? I was curious to know what a device equipped with Dolby Volume and dialnorm would do in the presence of metadata. The examples I gave were if the signal has metadata and dialnorm is set, does the audio pass through the Dolby Volume system unmolested? What about a signal that includes metadata where dialnorm is incorrectly set either through oversight or design? According to Dolby, both technologies can be implemented in the same consumer device and will be able to work in harmony but ultimately it depends on how the consumer product manufacturer implements the technologies and how the home user applies them.

It would seem appropriate that the implementation would first choose the metadata and then apply Dolby Volume only as a safeguard to prevent system overloads, speaker tears and shaking the trailer off the jacks. The consumer will have the ability in a Dolby Volume-equipped device to set a reference level. It is my understanding that as overall volume is raised or lowered, the spectral balance is maintained based on human hearing characteristics.

In summary, to maintain the best aural experience for the end users, continue to accurately apply dialog normalization (or start applying it, it drives me crazy when switching between football games). Don't think about Dolby Volume as any kind of a substitute for accurate audio processing but as a failsafe.